1. Field of the Invention
The invention is directed to an improved magnet valve suitable for use, for example, in hydraulic fluid systems.
2. Description of the Prior Art
A conventional magnet valve, in particular for a hydraulic unit, which is used for instance in an antilock system (ABS) or a traction control system (TCS) or an electronic stability program (ESP) system is shown in FIG. 7. As seen from FIG. 7, the conventional magnet valve 40, which is open when without current, has, besides a magnet assembly 5 with a cover disk 12, a valve cartridge, which includes a capsule 6, a valve insert 1, a tappet 20, a restoring spring 3, and an armature 7. In the production of the magnet valve 40, the capsule 6 and the valve insert 1 of the valve cartridge are joined together by pressing, and by means of a sealing weld 8, the valve cartridge is hydraulically sealed off from the atmosphere. In addition, the valve insert 1 absorbs the pressure forces that occur in the hydraulic system and conducts them onward via a calked flange 9 to a calked region, not shown, on a fluid block. The valve insert 1 also receives the so-called valve body 4, which includes a valve seat 10 into which the tappet 20 plunges in sealing fashion in order to accomplish the sealing function of the magnet valve 40. As also seen from FIG. 7, the tappet 20 and the restoring spring 3 are guided in the valve insert 1, and the tappet 20 is guided in a tappet guide 11 and the restoring spring 3 is radially guided and centered at one end on the tappet 20 and rests on a contact face 21, and at the other end rests, axially guided, on the valve body 4.
FIG. 8 shows a conventional exemplary embodiment of the tappet 20. As seen from FIG. 8, the conventional tappet 20 includes the axial contact face 21, a spring guide 22 onto which the restoring spring 3 is slipped and guided radially on the inside in the short region of the spring guide 22, and a tappet cone 23 with a transition region 24 between the spring guide 22 and a tappet dome 25, which plunges in sealing fashion into the valve seat 10. No further fixation or centering of the restoring spring 3 at its installation site is provided for. The flow path of the fluid through the magnet valve extends via the restoring spring 3, so that the spring force of the restoring spring 3 is operative in the region of the flow forces, which because of the flow are capable of acting on the turns of the restoring spring 3. If the order of magnitude of the spring force and the order of magnitude of the stiffness of the restoring spring 3 are within the range of the forces of the flow acting on the spring turns, unwanted influence on the spring behavior by the flow can occur. For instance, lifting of the restoring spring 3 from its contact with the valve body 4 can occur, which can be associated with a corresponding (force) action on the valve tappet 20 and unwanted influence on the valve function. The unguided portion of the restoring spring 3 can furthermore be laterally deflected or shifted, so that contacts and hence frictional forces can occur between the valve insert 1 and the tappet 20. Because of the frictional forces generated, the valve behavior can be adversely affected, and the tappet 20 may be damaged by the spring ends, which may have burrs.